The Indians called it Pay-hay-okee - river of grass. We call it the Everglades. The names suit the expansive savannah landscape that covers much of South Florida from Lake Okeechobee down through the Shark River slough into Florida Bay. Although sometimes it is referred to as the country's "last frontier," development has made deep inroads into the natural flow of this river. Still, the National Park Service lists 1,500,000 acres of the Everglades under its management, making it the third-largest park in the lower United States.

Driving into the park off US 1 some 30 miles south of Miami amid scudding, slate-gray clouds and intermittent showers, one could feel the force of this life-giving element that is so indispensable in providing diversity of life to this part of the world.

At first, one is not aware of the river flowing just below the base of the expansive fields of saw grass. However, at one of the pull-offs where the park service has built a looping boardwalk for observation, closer inspection reveals an almost imperceptible movement of clear water flowing southward to Florida Bay. Life abounds below the surface in the smallest detail, from the tiny blue gill to largemouth bass and Florida gar fish. Although we saw only one small snake swimming among the blades of grass, more than a dozen varieties of snakes and other reptiles, including several uncommon lizards, are found in the park.

Gazing from the observation platform, the eye takes in a broad sea of grass interrupted occasionally by islands of trees and scrub. These are called hammocks and are occasioned by a small degree of higher ground forming over limestone, thus allowing hardwoods such as gumbo limbo, royal palm, bald cypress, slash pine and a tangle of ferns, vines and air plants to take hold and grow. The tree islands provide cover and homes for marsh rabbit, muskrat, opossum and other small critters. White tail deer are in evidence, but the panther, once common in these parts, has been reduced to some 50 in all of Florida.

Alligators and crocodiles both inhabit the Everglades. Alligators prefer fresh-water sloughs where they can feed on fish, turtles, wading birds and other small animals, while the less numerous crocodiles favor the salt marshes and mangroves closer to Florida Bay. We saw several alligators, but only one crocodile swimming near the marina at Flamingo. By far the most visible animals in the park are birds. Some 300 species have been identified, but the most frequently seen are several types of egrets, the purple gallinule, anhinga or water turkey, several varieties of herons, roseate spoonbills and white ibis.

Underpinning the Everglades and extending throughout the Keys far below the surface are ancient rocks that geologists say once were part of the Appalachian Mountains. Far back in time the mountains were worn level, allowing the ocean to flow over them. Lime and sand built up gradually in layers over the centuries. The surface of this limestone buildup, known as Miami Oolite, forms the base under the Everglades. Various conditions brought on by rain and underground water pitted the oolite and formed the hammocks.

One of the more popular walking tours in the park is the Anhinga Trail. One morning my wife and I set out to see what wildlife might be visible. Our first sighting was an immature anhinga perched on a branch with wings fanned out drying in the warm sun. These birds are slender, with long necks and tails. Like the cormorant, they are excellent underwater swimmers. Several alligators were spotted across the slough, idling away the day.

Catching up with park ranger Kate Niblock, we learned the tiny turtle she was holding was a peninsula cooter, a fresh-water species. While looking over this little fellow's markings and in close proximity to where we were standing, we heard a soft cry, not unlike a puppy's low bark. Kate said it was a baby alligator seeking its mother, who couldn't be far off. All eyes turned toward the sound and we were rewarded with a glimpse of the young reptile swimming under the roots of a large tree. The little fellow was about 10 inches long and sported the distinctive

yellow bands of young gators.

About 50 yards beyond this encounter we were treated to the sight of a full-grown alligator lazing in shallow water. It looked to be about 9 or 10 feet long. The ranger judged it to be about 15 years old. Wading a short distance away, apparently oblivious to any danger, was a tri-colored heron. Turning away for a moment, we noticed an enormous grasshopper poised on the railing. We were told it was the lubber, the largest grasshopper found in the United States.

During an early morning visit to Eco Pond near our cabin, we saw squadrons of birds flying back from their offshore overnight roosting places in Florida Bay among thick mangrove islands. There were snowy and common egrets, great white herons, a few white ibis and a scattering of roseate spoonbills. Interspersed among the cries of the birds was the deep-throated croak of a bullfrog, punctuating the morning air from beneath the viewing platform.

Mangroves are somewhat like hammocks, but flourish along the coastal edges of the Everglades. We were able to explore these fascinating thickets first hand by hiring a guide at the Park Service's Gulf Coast Visitors Center in Everglades City. The thick, darkly compressed mangroves are composed of a vast profusion of vegetation undergrowth featuring clusters of black and red tropical trees with large roots fanning out like ribs of an umbrella. Thick spreads of branches supporting massive vines shelter a variety of wading birds that roost among them at night.

Our shallow-draft, flat-bottom boat with comfortable swivel seats was ideal for spotting wildlife. Before entering a densely twisting canal, known as Halfway Creek, our guide, Stanford Daniels, stopped the engine, enabling us to drift near a high mound of shells placed there by the Calusa Indians. Daniels said it was one of about 27 mounds in the area, added because the mud banks are so low to the water and difficult to live on. Not much is known about the Calusa, but they are believed to have inhabited the Everglades and Keys for thousands of years.

With the engine silent, we could hear the soft sounds of a manatee surfacing for a breath before spotting five or six snouts rhythmically rising and falling just out of camera range.

Low tide along the banks of Halfway Creek revealed rich, black mud anchoring the mangroves. Tiny colonies of crabs come out of their small holes to take advantage of the low water. Some scamper among the roots and on the overhanging branches that all but block the sky. The mangrove tree is the only tree than can excrete salt water. Tannin from the roots and decaying leaves color the water amber.

Our arrival flushed a small white ibis, distinguished by its curved beak. It is the only bird that can fly without difficulty through the choking underbrush of the mangroves. Our guide, a native of the area, said it is not clear if the creek was made by the Indians or created by nature. However, it was used by early pioneers in the 1890s for moonshining and during the 1970s for running drugs.

Driving across Big Cypress National Preserve along US 41, we stopped at the H.P. Williams wayside park for lunch. Finding the picnic tables exposed to the unrelenting heat of the midday sun, we opted for a low limestone wall running along a high bank overlooking a canal of some 30 yards in width. On the opposite side, bordering this small open body of water was a dense cluster of bald cypress trees. Several motionless anhingas perched high in the branches enjoying the sun. Far down the waterway we saw what we believed was the snout of an alligator.

To our delight, halfway through our sandwiches, another alligator swam into view, stopping below the wall. It must have gotten handouts from other travelers, despite a sign that warned it was against the law to feed alligators. Disappointed at our lack of generosity, it slowly swam away.

The Everglades, like much of the endangered wildlife within its environs, clings precariously to life from the threat of encroachment by thousands of new residents moving into southeastern Florida ever week, by over-development and the control of water coming into the park. We need to consider these irreversible effects before this remarkable national treasure disappears before our eyes.